The present invention relates to a process for lithographing thick layers, deposited on a solid substrate, of paste used in the hybrid circuit industry, for forming networks of very fine patterns and obtaining, by simple methods such as silk screen printing or coating with a squeegee, patterns having lateral dimensions as fine as those obtained by more sophisticated methods such as vacuum evaporation, for thin layers.
Two methods exist for forming networks of patterns on a solid and electrically insulating substrate. One is the method of thin layers which uses vacuum evaporation or cathode spraying of a solid, metal or alloy, the layer of which, from a few nanometers to a few micrometers thick is then chemically etched by a well known photolithographic process. The accuracy obtained, which is that of the photographic masks, is of the order of a micron along a dimension of the pattern parallel to the plane of the mask, but this method requires expensive deposition equipment. The other is the method of thick layers in which a layer of paste, from approximately one to 50 micrometers thick, is either spread with a squeegee or deposited by silk screen printing. The equipment for coating is less costly than the equipment for depositing thin layers, but the accuracy obtained, or more exactly the fineness of the patterns obtained, is limited by the minimum dimension of the mesh of the silk screen and is about 200 micrometers (125 micrometers in certain cases).